Field of the Invention
The present invention relates to upright vacuum cleaners having a base to which a handle is pivotally mounted. In particular respects, the disclosure relates to a base construction that permits free rotational movement of the airflow-carrying portion of the base.
Description of the Related Art
Vacuum cleaners have been provided in a variety of configurations. One common type is the upright vacuum cleaner, which has a base that moves on the floor, and a handle pivotally mounted to the base. The base includes a suction inlet that faces the floor. A vacuum fan and motor assembly (“suction motor”) is located in either the base or the handle, and fluidly connected to the inlet to generate a suction flow of air to draw in dirt and debris. A dirt collection device, such as a filter bag or inertial (e.g., cyclonic) separator, is provided in the base or, much more frequently, in the handle. In use, the handle is leaned back and manipulated to direct the base over the floor in a series of back-and-forth motions. The upright vacuum cleaner is stored by pivoting the handle to an upright position, where it remains by gravity (if leaned forward somewhat to put the center of gravity in front of the pivot axis) or with the help of an upright handle lock mechanism. The vacuum cleaner is also sometimes placed in the upright position during use, such as when the suction motor is connected to an auxiliary cleaning hose.
It is desirable to make sure the handle lock mechanism does not permit unwanted tipping, as such can be inconvenient and may cause damage. In more recent years, it has become increasingly common to position both the suction motor and the dirt collection device in the handle. This places more weight on the handle, and makes it even more important to securely hold the handle in the upright position. Typical handle lock mechanisms use a compact pedal-operated latch on the base, which engages a corresponding hole or shelf on the handle. Examples of such devices are shown in U.S. Pat. Nos. 4,423,534 and 6,006,401, which are incorporated herein by reference. Other handle locks use spring-loaded pins or shafts to retain the handle using an articulated spring-and-catch system that permits rotation after a sufficient force has been applied to press the spring-loaded catch out of engagement. Examples of these devices are shown in U.S. Pat. No. 5,353,471 and U.S. Publication No. 2009/0276975, which are incorporated herein by reference. In devices having a relatively heavy handle, the lock may be fairly robust to bear the weight of the handle, and multi-part spring-and-catch systems can be complicated and expensive to produce.
The base of a typical upright vacuum cleaner comprises a relatively robust structure that holds supporting wheels and the main suction inlet, and carries the entire weight of the handle. Height adjustment mechanisms have been provided to adjust the height of the suction inlet relative to the floor to thereby enhance performance on various different surfaces, ranging from hardwood floors to thick carpets. Height-adjustment devices typically comprise a small wheel assembly, located just behind the suction inlet, that is moved up and down relative to the rest of the base to raise and lower the suction inlet. The wheel assembly typically bears a large portion of the base's weight, and is the first structural part of the device to strike obstacles on the floor, and therefore must be fairly strong and durable.
FIG. 7 illustrates a typical prior art upright vacuum cleaner 700. The vacuum cleaner 700 has a base 702 and a handle 704 pivotally mounted on the base 702 to rotate about a pivot axis 706. The base 702 includes rear wheels 708 and front wheels 710, which provide the primary support function to hold the vacuum cleaner 700 during storage and use. The front wheels 710 may be mounted on a wheel carriage 712 that rotates to raise and lower a suction inlet 714 located at the front of the base 702. For example, lowering the front wheels 710 relative to the rest of the base 702 raises the suction inlet 714 relative to a surface 716 upon which the wheels 708, 710 rest. In this typical construction, the base 702 comprises a unitary rigid structure that joins the front and rear wheels 710, 708, handle pivot 706 and suction inlet 714. Such a design has long been considered favorable because it provides strength, simplicity, and low manufacturing cost. In use, the user pushes the vacuum cleaner 700 forward by applying an operating force F1 to the handle 704, and then pulling backwards with an opposite force. It is now believed that such devices have dynamic characteristics that can, under some circumstances, lead to more difficult operation.
While various features of upright vacuum cleaners like the ones described above have been used in the art, there still exists a need to provide alternatives to such devices.